246 THE HEART, BY F. SCHWEIGGER-SEIDEL. 



luntary muscles. Weismann* first established, from extended re- 

 searches in comparative anatomy, that the relations in question 

 are not the same for all the Vertebrata. In Lizards, Amphibia, 

 and Fishes he found the several segments of the cardiac muscula- 

 ture to be formed of closely approximated elongated and fusiform 

 cells, the substance of which presented transverse striae (fig. 43). 

 In Mammals, Birds, and Reptiles, on the other hand, although 

 an analogous cellular structure could be demonstrated during the 

 embryonic period, yet the anastomosing fibres of the heart must 

 always, he thought, be regarded as formed from the coalescence 

 of isolated cells. Kolliker and Aebyf- opposed this view, and 

 the latter observer even found the muscular fibres of adults 

 to be divided into separate portions by transverse septa. But 

 Eberth| has recently made an important step in advance, by 

 showing that in two of the above-named groups of Vertebrata 

 a separation of the several cells from one another occurs' in the 

 fully developed condition of the muscular tissue of the heart ; 

 so that what was commonly regarded as a single fibre turns 

 out to be a complex structure composed of one or many nu- 

 cleated transversely striated muscle cells. Here, therefore, in 

 opposition to the term fibres, applied to the structural elements 

 of the ordinary muscles of the trunk, we may speak of chains 

 of muscle cells or muscle-cell trabeculae. The difference above 

 referred to between the several groups of animals amounts only 

 to a dissimilar mode of arrangement of the muscle cells, the 

 independency of which in the heart still remains certain. As a 

 proof of this statement, it happens that especially in Mammals 

 we are able to render the limits of the several cells apparent, 

 and to obtain these in an isolated state. The best means for 



* Archiv fur Anatomie und Physiologic, 1861, p. 42. 



t Zeitschriftfur rationelle Medicin, 3 R., Band xvii., p. 195. 



J Virchow's Archiv, Band xxxvii., p. 100. 



As long as a division of the cells from, one another can be generally 

 demonstrated we can obtain no correct estimate of the degree of coalescence 

 that has taken place ; hence it is not easy to discover the difference that 

 exists between the statements made by Kolliker in the fifth edition of his 

 Handbuch der Gewebelehre, and those advanced by Eberth. Kolliker 

 now admits that the coalescence of the cells is somewhat less intimate than 

 he had stated it to be. 



